ffmpeg v0.8 has changed progress format.

[snahor]

It's using 00:00:00.00 format.

[Cruel]

Your fix seems to work, but for compatibility, perhaps it would be better to have this:

try:
    progress_callback( float(progress_match.group(1)) * 1000, duration )
except ValueError:
    # Your code

ValueError was the one thrown for me when it tried to typecast to float, so that way it still works on older ffmpeg too (which I personally need).